1. Field of the Invention
The present invention relates to an air bag expanding and deploying due to an inflow of gas, and an air bag apparatus.
2. Description of the Related Art
Conventionally, there has been known, for example, an air bag apparatus provided in a steering wheel of a motor vehicle. The air bag apparatus is provided with an air bag body formed in a flat bag shape, a cover covering the air bag body, an inflator injecting gas, and the like. Then, the air bag body is folded to be small in accordance with a certain method at unactivated state so as to be received inside the cover. At a time of detecting an impact of collision by a collision sensor, the air bag body is expanded by injecting the gas from the inflator. The cover is broken due to an expansion pressure of the air bag body and the air bag body is protruded, expanded and deployed to face the passenger, so that the impact of the collision to a passenger is reduced.
The air bag body has been conventionally folded along a straight line at a predetermined position from a state being expanded on a flat plate so as to be formed in a rectangular parallelepiped shape capable of being received in the cover. However, there is a problem that it is hard to mechanically produce the folded air bag body, a lot of labor is required and it is hard to improve the productivity.
In order to improve the above mentioned points, as a folding method suitable for automation, for example, there has been known a structure shown in International Patent Publication Laid-Open No. WO97/48580. In particular, the air bag body is expanded during a folding process by using a folding apparatus provided with a folding plate arranged so as to form a coaxial circle shape or a spiral shape in opposition to each other from upper and lower portions of the air bag body. The air bag body is folded by gripping the air bag body by the folding plates, and moving or deforming the folding plates toward a predetermined hollow space so as to reduce radial distance between each of adjacent folding plates. However, in this structure, there is a problem that the structure of the apparatus becomes complex and it is not easy to reduce the production cost.
Further, with respect to, for example, the air bag body formed in a flat circular shape, there has been proposed a so-called petal fold in which the air bag body is collected toward a center from an outer peripheral portion thereof so as to form a pleat shape. With respect to this method, there have been known structures described in Japanese Patent Publication Laid-Open Nos. 10-129381, 10-217894 and the like.
At present, there is required a structure of an air bag body which can improve the deploying characteristic and reduce the production cost.
The present invention is made by taking the points mentioned above into consideration, and an object of the present invention is to provide an air bag and an air bag apparatus in which the deploying characteristic of the airbag is improved and the production cost can be reduced.
The first aspect of the invention provides an air bag comprising: a first surface portion with an inlet port through which gas is introduced into the air bag; a second surface portion opposed to the first surface portion; wherein the first surface portion and the second surface portion are respectively accumulated and folded in a pleat-like fold toward the inlet port with the surface portions being substantially detached from each other, a plurality of tab portions formed along the inlet port in a spiral shape, the first surface portion and the second surface portion linearly opposed to each other at the tab portions.
The second aspect of the invention provides an air bag apparatus comprising: an air bag body; an accommodating container receiving an folded air bag and being breakable at a predetermined condition, the air bag comprising: a first surface portion with an inlet port through which gas is introduced into the air bag; a second surface portion opposed to the first surface portion; wherein the first surface portion and the second surface portion are respectively accumulated and folded in pleats toward the inlet port with the surface portions being substantially detached from each other, a plurality of tab portions formed along the inlet port in a spiral shape, the first surface portion and the second surface portion linearly opposed to each other at the tab portions.
The third aspect of the invention provides an air bag according to aforementioned aspects of the invention, wherein the second surface portion is formed in a substantially single layer at a part opposing to the inlet port of the first surface portion, wherein the second surface portion includes a portion opposing to the inlet port of the first surface portion and has a front surface deploying portion deployable in a direction to a front side of the air bag, wherein the first surface portion is opposed to and is substantially detached from the second surface portion at a part distant from the inlet port, and wherein the front surface deploying portion is accumulated and folded toward the inlet port without substantially engaging with the tab portion, and is deployable in a direction moving apart from the inlet port.
According to aforementioned aspects of the invention, at the tab portion, the gas is smoothly supplied to an end portion of the tab portion along the linearly opposing portion, and the tab portion is deployed so as to be unwound. Accordingly, the gas introduced from the inlet port is smoothly supplied to a peripheral edge portion, and the deploying characteristic of the air bag body is improved. Further, the front surface deploying portion can rapidly deploy to a side of the breaking portion immediately after the inflow of the gas, to break the cover covering the folded air bag body and efficiently deploy the air bag body.